FWIW, I was already about 50 years old then, and hadn't shot anything but cameras, shotguns and a 22 rifle for years. I didn't start carrying until about 4 or 5 years ago, when I thought it the best idea considering my vulnerability when working in certain less safe places at less safe times. Until then, I carried only a pocket knife or a Leatherman, neither of which offered much protection. That was the case on 9/11 as well.
By coincidence I was home that day and was a long distance viewer of the awful event. I was usually at work at about 8am, but that day I had to stay home, because I was to meet and set up a crew that was going to replace the windows and siding on my house at that time. While waiting for them, I had the Fox morning show on the TV in the kitchen. I wasn't paying much attention, as I was talking to one of my employees on the phone giving him directions for a photo shoot setup to be constructed in my studio that day. But then, I noticed the TV people started to make some ominous sounding noises about a plane crashing into one the twin towers, so I got off the phone and paid attention. They explained that a small private plane pilot had likely been blinded by the morning sun reflecting off the building and crashed into the side of the one tower. I immediately thought this sounded highly unlikely, and when I saw the hole in the building and fire, I thought that that looked to be a ridiculous explanation, given the size of the hole and the size and isolation of the tower. The pilot would have had to be literally blind for 10 minutes and flying a much bigger plane. While I was muttering to myself with suspicion and ridicule for the TV readers who would accept such an idiotic idea, they had a wide shot of both towers on the screen. Then it happened. Another plane flew into the frame and smacked into the second tower, and it was obvious right then that it was a very large airliner and left no doubt that both hits had been planned and purposeful. It didn't take a genius, given the history of Islamists trying to bring the Towers down years earlier, to understand what had just happened and its significance, but I didn't right away know just how terrible the human loss would yet be until a while later.
Not waiting any longer, I went outside to greet the window and siding guys. The first thing I told them, after finding out that they weren't listening to their truck radio on the way over, was about the towers and that there was no question but that we were now at war, a real shooting war. The Pentagon, Flight 93's heroic nosedive and crash in Pennsylvania, all happened after I went back inside to be glued to that little TV in my kitchen until I had to go to work in the afternoon. It was so terrible for those killed by the fire, explosions and "deathjumps", and so tragic and sad for the families of the slain. Those hijackers' comrades and leaders deserved all the destruction that we levied against them and a lot more. Unfortunately we struck back at a lot of people that weren't responsible and missed a lot that were. I guess that's just about how it always goes nowadays.
The memory of this will never leave me until the day I die.